Rey is one of the most ancient region of Iran and currently it is known as Rey county in Tehran province. The history of its foundation dates back to pre-historic times. The history of it becoming a human habitation dates back to 3000 years BC. During pre-Islamic times, Rey was a great center for Zoroastrian religion and the Zoroastrian priests had established a kind of religious government similar to Vatican City. Overall, Rey was considered a holy city during the Median and Achaemenian dynasties and maybe even before those.
Rey is the only archeological region in Tehran province, which has many historical monuments and interesting locations. This region is also considered as the center for development of religious tourism in Tehran province. Historical attractions of Rey county overshadow the natural attractions of the region.